Since Sakatha has been defeated, and his lair is gone, we did a little spoiler-filled recap at the end of the game session. I rarely do this except post-campaign, but I think it was appropriate to do it now since nothing from it will impact play.
One reason I made Sakatha a load-bearing monster was because I didn't want the party to keep coming back to the Cold Fens over and over and over again, "just making sure" and "maybe we missed something" and "this time we'll check with a guy with See Secrets and Per 19, not just Per 18" in the hopes of findng something. So I set it up so that can't happen once the main guy is gone. I made it a relatively slow collapse so the PCs would have time to loot, but not to linger. Had I made it shorter, they wouldn't have had time to loot. They barely did, and really maximized "guard the group" over "get the loot." The next load-bearing monster (there are others) might not be so forgiving. You can't always search the room with a maximum bonus while everyone heals, recovers FP, and otherwise takes their ease until fully ready to delve.
Sakatha's Trident was an oversized balanced trident with Accuracy +2 and Puissance +2. $40,800 base value, saleable for at least $16,320. Broken by the PCs because delvers always assume you need to break stuff to win fights. It was useful to disarm him, but they had all the tools to defeat him without this step.
Speaking of killing Sakatha, my players especially depend on getting foes to reveal their weaknesses. They'll threaten or attack a foe, and hope that will prompt a foe to give a clue to their weak point. This can work sometimes, but doesn't always. It works less often than it succeeds. They also want to get feedback on success instantly. They'll fill a foe's hex with fire, and, before anything else happens, expect the foe to give away how vulnerable they are to fire so they can pile more on. I feel like I say, "It's a one-second turn" so often I should have it on an audio loop. Sakatha didn't give much away. And why should he have? My players will likely chime in here saying they didn't really expect him to, but they had to try, and had to observe just in case . . . but that's rationalizing behavior despite a lack of success in doing so. These are the same guys who want to Dodge shots when they have Missile Shield up so the enemy thinks they don't and wastes attacks. This also assumes the foe knows something to give away - picture Achilles, confident that he's unkillable, not realizing his heel is vulnerable. Would he flinch badly at an attack on his heel, or just arrogantly attack you back until that last lucky shot that puts him down?
Further, speaking of killing Sakatha, clues to the best way to kill him were upstairs - murals on both of the triangle side rooms in the triangular building, and in a cryptic note about Sakatha held by the bandit wizard. He left it behind accidentally, but the PCs literally never checked the hallway where the secret door was after just moving through it quickly once. So that was never found. They even skipped that side hallway during a session when they otherwise went everywhere else with Galen (Per 18) with See Secrets on.
Speaking of that bandit wizard, had they managed to crush the bandits a session or two earlier back in the day, and get the wizard, they could have found the loot of the bandits. They didn't, and the wizard left with the loot. And wearing Hooded Robes of Protection. Caution costs chances.
And missed treasure? They never tried to track down where the wights came from, either to finish them after a victorious fight or after exterminating them. In fact, they moved fast to avoid them specifically, even after wiping them out . . . and "avoided" them by traveling the exact same way to and from the triangular building ever time. Anyway, there was a clear "lair" for the boss wight. In it were a skeleton (I won't say of whom or what) with some mundane loot and an Necklace of the Serpent in the form of a silver necklace with a green jade symbol of two snakes facing each other over a rising sun. El Murik's player would have loved that. There was also, in one of the acid vats, a suit of corrosion-proof mail - which eventually made it into DFRPG Magic Items as an armor enchantment. Plus, their mundane gear was recovered and thrown into a side room the PCs never bothered to find.
There were other treasures, magical and mundane, and some fun challenges. Mostly, though, there were a lot of missed opportunities. Often lost due to a little too much caution when caution wasn't called for. Again, this stuff is why I made Sakatha load-bearing. I didn't want to deal with this place being a permanent campaign fixture for parties unwilling to delve deeper in Felltower. The looted-out Caves of Chaos and repeatedly sacked Lost City still get some "we should go and check this out" discussion, and I wanted this off the table.
Finally, the marshy part of the Cold Fens, the lair of Sakatha, the name, and very much of the main details of the area came directly from I2 Tomb of the Lizard King by Mark Ayres. In it, Sakatha is a vampiric version of the Lizard King from Fiend Folio. I liked the idea a lot, but I didn't need another vampire. I needed a demonic lizard man to match the depictions I'd had on the wall near the temple in Felltower. So I changed things around to make it so.